Field of the Invention
The present invention relates to a method of fabricating a sample support membrane.
Description of Related Art
Sample support membranes used in transmission electron microscopy (TEM) and other similar applications are made of carbon film, silicon nitride film (SiN), and Formvar (polyvinyl formal resin). Preferably, sample support membranes satisfy various conditions including electron beam transmittance, ease of manufacturability, invulnerability to electron beam irradiation, and surface smoothness. A related art method of fabricating a sample support membrane is described below.
Where a carbon film is used as a sample support membrane, it can be fabricated by depositing carbon on a cleavage face of mica or rock salt using a vacuum evaporator, peeling off the evaporated carbon film on a water surface, and scooping the water using a finely apertured mesh or a microgrid.
Where a sample support membrane is made of Formvar, a clean slide glass or a cleavage face of mica is first set on equipment for fabricating a Formvar membrane. The slide glass is immersed in dissolved Formvar, forming a membrane on the slide glass. Then, in order to peel off the membrane from the slide glass surface, a cut is formed in the surface of the membrane with a razor. The slide glass is slowly sunk in the liquid at an angle of about 10 degrees to the water surface while holding one end of the slide glass with one hand. Consequently, water enters between the membrane and the glass, peeling off the membrane. The membrane floats on the water surface. The membrane is scooped with a mesh or microgrid, thus fabricating a sample support membrane.
JP-A-2009-517685 discloses a method of fabricating an ultrathin carbon support membrane for high-resolution TEM analysis, the method involving four phases. The first phase consists of placing a clean, hydrophobic slide glass on an ice pack located in a cooled refrigerator or freezer, picking up the slide glass with tweezers, and exposing the glass to the atmosphere to form liquid droplets. The second phase consists of dissolving Formvar in chloroform solvent to form a solution, immersing the slide glass having the liquid droplets thereon in the solution, picking up the glass out of the solution after several seconds, applying moisture absorbing paper to the bottom, and placing the glass vertically within the atmosphere to dry the glass. The third phase consists of setting the polymer film formed on the slide glass afloat on the surface of distilled water using the surface tension of the distilled water and placing a Cu grid being one type of metal mesh grid on the polymer film that has been placed on the surface of the distilled water. The fourth phase consists of taking out the polymer film from the distilled water using a hydrophobic support stage such as paraffin film, then placing the polymer film in a higher position, and coating the film with carbon.
In the above-described method of fabricating a sample support membrane, the membrane is formed using peeling at a water surface. However, this peeling must be done manually. Furthermore, if peeling is done at a water surface or when the membrane is placed on a mesh, the membrane might be destroyed. In this way, with the method of fabricating a sample support membrane using peeling at a water surface, it is not easy to fabricate a sample support membrane.